package mid;

import org.junit.Test;

public class a451_根据字符出现频率排序 {
    public String frequencySort(String s) {
        if(s.length()==0){
            return null;
        }
        int[] counts = new int[128];
        char[] chars=s.toCharArray();
        for(int i=0;i<s.length();i++) {
            counts[chars[i] - 'A']++;
        }
        return s;
    }
    @Test
    public void tets(){
        String s="abcdd";
        frequencySort(s);
    }
}
